Incorporated into the rear suspension of heavy duty vehicular equipment such as refuse trucks, cement mixers and dump trucks is a component commonly referred to as a walking beam. Those heavy duty vehicles which incorporate walking beams typically include a pair used in conjunction with the rear tandem axles of the vehicle. The inclusion of the walking beams in the suspension system is made necessary by the extremely high weight loads which are typically exerted on the vehicle frame of such heavy duty vehicles.
Each of the two (2) walking beams incorporated into the vehicle suspension has an elongate configuration and defines a pair of apertures extending laterally through the opposed ends portions thereof. Additionally, extending laterally through the approximate center of each walking beam is a central aperture. The walking beams are connected to a pair of center beams of the vehicle via an elongate shaft, the opposed ends of which are extended through the axially aligned central apertures of the walking beams. Each walking beam is extended between and bolted to a pair of hanger brackets which are attached to the rear tandem axle housings of the vehicle.
The walking beam typically includes a pair of identically configured end bushings which are disposed within the apertures located adjacent the opposed ends thereof. In walking beam assemblies as currently known and manufactured, each of the two end bushings comprises a concentric pair of tubular steel sleeves having a layer of rubber therebetween. The outer diameter of the outer sleeve slightly exceeds the diameter of the walking beam aperture into which the end bushing is inserted. As such, each of the two end bushings is typically press-fit into a respective aperture of the walking beam via the utilization of a heavy tonnage press or similar device. The overall length of the outer sleeve slightly exceeds the depth of the walking beam aperture, with the inner sleeve having a length greater than the outer sleeve. Thus, when each end bushing is press-fit into a respective aperture, the opposed ends of the outer sleeve protrude slightly axially from each end of the aperture into which the end bushing is inserted, with the opposed ends of the inner sleeve protruding axially outward from each end of the outer sleeve. When the walking beams are attached to the vehicle frame via the center beam, the inner sleeves of the end bushings of one walking beam of the pair are coaxially aligned with respective ones of the inner sleeves of the end bushings of the other walking beam of the pair.
Subsequent to the press fit of the end bushings into the walking beams and the attachment thereof to the vehicle frame in the aforementioned manner, the rear tandem axles are extended through respective ones of the axle housings. The hanger brackets of each pair between which each walking beam is extended are provided with apertures to accommodate the fastening bolts used to attach the end bushings thereto. Examples of prior art walking beams include those sold by Hendrickson as Model Nos. 6969 and 45900 as well as those sold by Navistar as Model Nos. 124865R1 and 124892R1. Additionally, examples of end bushings commonly utilized include those sold by Hendrickson as Model No. 29878-1, and those sold by Euclid as Model Nos. E-1341A and E-2771.
When each walking beam is mounted between a respective pair of hanger brackets, the brackets themselves, which are typically U-shaped, initially come into contact with only the inner sleeves of the end bushings. However, over extended periods of time, the layer of rubber disposed intermediate the inner and outer sleeves of the end bushings will wear and dry out (i.e., crack and degrade), thereby allowing the outer sleeve, and hence the walking beam into which the outer sleeve is press fit, to chatter (i.e., move relative the rubber layer and travel radially and laterally therealong). Such movement typically results in a decrease of vibration dampening, and oftentimes results in the rear tires rubbing the chassis of the vehicle, particularly during turns. As such, the wearing of the rubber layer gives rise to overall diminished vehicle handling as well as increased wear of the remaining components of the suspension.
In walking beam assemblies as currently known and manufactured, once one or both of the two end bushings disposed within the walking beam become worn, the walking beam must be removed from the vehicle and the end bushings removed from therewithin. As will be recognized, due to the loss of elasticity in the rubber layer, both the rubber layer and the inner sleeve are easily removed from within the walking beam. However, the removal of the existing outer sleeve of the end bushing from within its respective aperture presents a significantly more difficult task, and generally requires the utilization of a heavy ton press (e.g., 80-100 tons) to remove the outer sleeve from within the aperture. Thereafter, a new end bushing must be press-fit into the walking beam in the aforementioned manner, which is also a difficult and time-consuming task. As can be appreciated, the costs associated with the repair procedure would be significantly decreased if the end bushings of the walking beam could be removed and replaced without the necessity of having to utilize a heavy tonnage press. Thus, there exists a need in the art for a walking beam assembly wherein the end bushings are adapted to be easily and quickly replaceable.